The past few weeks I have been hacking on another feature in Qt. Going with the theme of making Qt 4.5 faster I added a cache system to QNetworkAccessManager and provided a simple QNetworkDiskCache that can be used by most applications. Under the hood the new http backend has been enhanced to support all the http rfc cache features you would expect (even behave better than FireFox in one case). Adding a cache system is very important to a lot of our customers.

- Anyone who wants to use rss/atom feeds absolutely must have a cache system in place.
- Anyone who uses QtWebKit has been looking forward to a cache system.
- Any other application that pulls down files off the network such as in XMLPatterns can use the cache to improve performance and reduce network overhead.

To store the cache QDesktopServices::storageLocation has a new enum CacheLocation that can be used to determine a proper cross platform location for where cache files can be stored. The included QNetworkDiskCache is simple and should be good enough for a lot of customers, but for those that want to write a highly optimized one for small devices or to hook into another cache system (such as MSIE’s) the interface QAbstractNetworkCache is provided so you can implement custom cache systems.

For many applications enabling the cache will be as simple as:
QNetworkDiskCache *diskCache = new QNetworkDiskCache(this);
QString location = QDesktopServices::storageLocation(QDesktopServices::CacheLocation);
diskCache->setCacheDirectory(location);
networkAccessManager->setCache(diskCache);

To see it in action you can checkout the demo browser the 4.5 snapshots where I have enabled it.

Some of my colleagues on the graphics team have been writing graphics dojo demos with impressive speed and with a rainy weekend I thought I’d get into the action.
As I’m regarded as the text guy I thought it would be fitting to have a demo that uses text, so I made a text effect class that animates text fading in and fading out.

One thing that I see a lot of people do is that if they want to zoom into text, they change the fontsize. There is a fundamental problem with that approach as text doesn’t scale linearly (due to hinting). So in Qt4 we have a much simpler and more powerful way of scaling text that fits better in graphics concepts. You simply scale the QPainter during painting.
This means that if you call myPainter.scale(2,2); your 12pt font will suddenly appear as a nicely scaled 24pt font. Or, more accurately, it will show the original text at 200% zoom.

This is very simple and due to us reusing the same font settings we avoid recalculation and text layout. So it will actually be quite fast. So fast that you can animate it quite smoothly. As is shown in the demo.

There is not much more to say about it, so just grab the code and run it!
svn checkout svn://labs.trolltech.com/svn/graphics/dojo/zoomingtext

New business cards (not arrived yet). New employee badge (photo looks bad, as always). New email address (@nokia.com). New phone (starts with N). New intranet (huge). New Desktop (KDE 4.1 - I’m so impressed by you guys). New presentation templates (for my Akademy presentation). New marital status. New version control system (git).

And a new patch to make Qt 4.4 build within the LSB 3.2 environment, we’re getting very close to having one binary Qt/X11 Linux version to rule all distributions (bye bye distribution pain): lsb3.2-20080801.patch

Disclaimer: The patch above is unsupported, please contact my first name dot last name at domain starting with N for questions.

Since the Windows CE platform is still missing support for Phonon in 4.4, we are working on Phonon for this new Qt platform. We ported the Direct Show backend to Windows Mobile. Sadly there are only very few Direct Show filters available by default on Windows Mobile. But there is nothing we can do about this from the Qt side.

Because not all Windows CE SDKs and Devices support Direct Show, I also wrote a backend for the
Wave Form API from Windows CE. This backend has a lower footprint, but is for now only able to play wave files.

If you want to try out Phonon for Windows CE, then check out the Qt main snapshots, and either configure your Qt/Windows CE build with Phonon enabled (configure -platform win32-msvc2005 -xplatform wincewm50pocket-msvc2005 -phonon) or build Phonon manually (src\phonon).

While playing around with Phonon do not forget to deploy phonon and the plugin for the backend you want to use.

For people, who are not familiar with Phonon. Playing a wave file with Phonon just takes two lines of code:

Phonon::MediaObject *music = Phonon::createPlayer(Phonon::MusicCategory, Phonon::MediaSource("test.wav"));
music->play();

The Windows CE team is always happy to receive feedback. You can subscribe the qt-wince-interest mailing list by sending the word “subscribe” in the subject of a message to qt-wince-interest-subscribe@trolltech.com.

For this episode of the graphics dojo I’ve implemented the classic radial blur effect. The core radial blur effect is implemented with per-pixel manipulation, which Qt lets us do quite elegantly using the QImage class. The final dojo example uses the radial blur effect in combination with scrolling text drawn using QPainter to create a nice visual impression. Below is a screenshot of the effect as well as a recording:

Radial blur movie capture

As usual, the source code is available from the SVN repository: svn checkout svn://labs.trolltech.com/svn/graphics/dojo/radialblur

Qt released

Since the saying “The release is not out until you blog about it” is still in effect, I have the pleasure of announcing that Qt 4.4.1 has been released.

Here’s the download button:

The 4.4.1 release is a patch-level release, meaning it’s a bug-fix release on top of Qt 4.4.0, maintaining both forward and backwards compatibility. It’s a drop-in replacement for Qt 4.4.0 and shouldn’t cause you any problems.

The full changelog can be found on our website.

This release happened about a month later than I had originally planned to. We postponed it until we could make sure that 4.4.1 is better than 4.4.0. Also, we can find explanations relating to Summer in Norway:

• Key people leaving for vacations
• Scheduled power supply cuts
• Air conditioning machines being turned off in our building
• Temperatures in Norway being quite high this year (often reaching 30°C)

And you thought that Winter in Norway was a problem…

KDE 4.1 released

Of course, I couldn’t let it pass that KDE 4.1 has been released, dedicated to KDE long-time contributor Uwe Thiem. Uwe had been doing a great job spreading Open Source and Free Software in Africa (Namibia to be precise). And many would say that’s where it’s needed the most.

In any case, KDE 4 has come a long way since the 4.0 release back in January. Back then, applications were great; the desktop was shiny and new, but limited. Many things I was used to simply didn’t work. Even for a long-time KDE contributor such as myself, it was hard to let the good, old KDE 3.5 go. But ever since KDE 2.2, I’ve always used the bleeding edge version. If using it back then wasn’t a problem, today is should be even less.

But that’s old history! Six months have passed!

KDE 4.1 is a lot better today. Many of the things that people complained about in Plasma have been fixed. And, of course, the applications that were already great got even better. Everyone deserves a praise for their work, however minor their contributions might have been. (I submitted only a few crash fixes)

Sure, it’s not perfect — nothing is. However, given the pace of development, I’m sure those things will get sorted out quite soon.

We’re going to Akademy

Yes, the Trolls/Nokians will be going to Akademy 2008.

The following developing Trolls will be coming: Andreas Aardal Hanssen, Daniel Molkentin, Daniel Teske, Harald Fernengel, Jesper Thomschütz, Kent Hansen, Lars Knoll, Marius Bugge Monsen, Matthias Ettrich, Olivier Goffart, Oswald Buddenhagen, Simon Hausmann, Thomas Cooksey, Thomas Zander, and I. Most of those had to learn how to use the new Nokia Travel Planner in the last week.

Besides those, there will be other Nokians coming from all parts of the globe. I know of people coming from Finland and from Brazil.

Hope to see you in Belgium!

And for those who can’t come to Akademy, save the date:
Qt Developer Days 2008
MUNICH, Germany: October 14th – 15th
REDWOOD CITY, California: October 29th – 30th

A while back we announced the research project Qt Jambi AWT Bridge which allows you to mix AWT/Swing components and Qt widgets in the same window on Windows and Linux.

There were a few issues with the original version. The main problems were the fact that your window would be deactivated by the window manager when you clicked inside an embedded widget, some issues with unnecessary whitespace around the embedded components when you embedded AWT inside of Qt, and some people experienced a race condition which caused the embedded widgets to sometimes disappear.

The project has now largely been rewritten to be more robust, and both the window activation issues and whitespace issues have been resolved. If you sync the latest version from Subversion, you should be able to see major improvements. There are still some issues with keyboard focus (tabbing between the application widgets and the embedded widgets) which we are trying to resolve.

The sequence of commands to build has also changed. Please follow the following steps in order to build the project from source (for users of a binary package of Qt Jambi, we will try to get binaries for the bridge up at some point.) The following steps will only work if you have also built Qt Jambi from source.

Windows (Replace “nmake” with the “make”-application of your choice.)
set JAMBIDIR=\path\to\jambi\source\package
set JAVADIR=\path\to\java\sdk
.\generatorstep.bat
qmake
nmake

Linux
export JAMBIDIR=/path/to/jambi/source/package
export JAVADIR=/path/java/sdk
./generatorstep.sh
qmake
make

That should take care of building the native binaries. Then put Qt Jambi in your class path and compile all the .java files:

javac com/trolltech/research/qtjambiawtbridge/generated/*.java
javac com/trolltech/research/qtjambiawtbridge/*.java
javac com/trolltech/research/qtjambiawtbridge/examples/*.java

There are two examples in the com.trolltech.research.qtjambiawtbridge.examples package: QtInAwt and AwtInQt. These are the same as before, and show, respectively, how to integrate a Qt widget in an AWT frame, and how to integrate an AWT component in a Qt widget. Here’s a screen shot of QtInAwt:

The window here is handled by AWT, the two input fields and labels for the name are Swing components, and the entire bottom part is a layout created in Qt Jambi.

Please go to the project homepage for more information.

Distorting the geometry of an image with a specific periodic pattern can give the illusion of being underwater. This trick was for example employed in the very first version of Quake, either to oscillate the water surface or to modify the view when you jump inside the water. Apparently, it is not difficult to do that, even with pixel-per-pixel manipulation of QImage.

Check out the code from the usual place:

svn checkout svn://labs.trolltech.com/svn/graphics/dojo/underwater

It is recommended to build the program and see the effect by yourself, the following screenshot can hardly describe the animation. As usual, once the example is running (it would show the included bridge picture), you can change the picture by dragging an image (from local disk or a web browser, e.g. Flickr or Picasa Web) and dropping it on the main window.

Note: the snappers picture is from james_wicks, distributed under the Creative Commons Attribution 2.0 Generic.

Hi there. Introducing myself, my name is Friedemann Kleint, and I am one of the trolls hacking away at Qt Designer at the Berlin Office.

Today, I would like to draw your attention to the QFormLayout class. This is a special layout class suited to the common descriptive label - control arrangement found in many dialogs. It thas been developed in cooperation between Brisbane, Oslo and Berlin.

A typical form layout looks like this:

Note how the layout takes care of the label alignment according to the platform style. By the way, did you know that you can open several previews in different styles in Designer to compare them?

At first sight, QFormLayout looks like an ordinary grid. However, the layout also has policies for wrapping rows when it shrinks. For example, when setting the property rowWrapPolicy to WrapLongRows, we might get:

Let’s first have a look at the code. You might have created a such dialogs using QGridLayout, previously. This required some housekeeping of the current row. This is no longer necessary with QFormLayout using the addRow() convencience function. You don’t have to explicitly create the label, either:

QFormLayout *formLayout = new QFormLayout;
formLayout->addRow("Name", new QLineEdit);

For completeness, there is a setWidget() function which allows you to address single cells. It takes a row parameter and an ItemRole enumeration, which can be one of QFormLayout::LabelRole or QFormLayout::FieldRole.

In Qt Designer, you can create such arrangements as would in the case of a QGridLayout; you place the controls on a form and choose “Lay Out in a Form Layout”.

Hint: If you have existing .ui files containing such 2-column grid layouts and want to migrate them to the form layout, it might be sufficient to just replace the layout element <layout class="QGridLayout" name="gridLayout" ></layout> by something like <layout class="QFormLayout" name="formLayout" ></layout> (after making a backup copy, of course ).

It is also possible to create arrangements with controls that span the 2 columns. This let’s you add controls with long labels (for example QComboBox) or QGroupBox elements. It can also be used to partition the form layout into sections by using spanning QLabel elements:

In code, you would use the addRow() overload that takes just one QWidget* parameter.

In the upcoming 4.5 release, this functionality will also be available in Designer. Lonesone widgets on a QFormLayout get an active left/right resize handle that let’s you change the span:

The per-cell API of the QFormLayout uses the SpanningRole enumeration value of ItemRole to handle these rows.

Summarizing, the QFormLayout should be used whereever the typical descriptive label - control arrangement occurs. The dialog will then look correctly on a all platforms.

Time for another fresh example for the Graphics Dojo. This time I present a small tool that does nothing but showing the famous HSV cylinder. To give some realism, subtle blurred reflection is also added but can be easily disabled. Manual full-scene anti-aliasing is provided by the usual multisampling approach. Everything is done using pure QImage per-pixel manipulation along with some tricks, no OpenGL (or even its GLSL) is involved.

For the code, check it out using:

svn checkout svn://labs.trolltech.com/svn/graphics/dojo/hsvpie

Note that the tool is not optimized for speed (evidenced by lots of setPixel() calls) so there is definitely room for improvement. Some possible further enhancements left as exercises for the readers are interactivity (mouse dragging to change e.g. the depth of the pie) and threaded rendering (so that the application remains responsive, just adapt the Mandelbrot example).

Have some dojo-fun!